The Peca Computing Sight

The American version of the 40mm Bofors AA gun was often equipped with one of two different computing gun sights for on-carriage fire control. A computing sight mechanically calculated a firing lead and physically adjusted the sights to assist the gun pointers in more accurate aiming. Both the British Stiffkey Stick and the more sophisticated M7 computing sight, better known as the Weissight, were widely used by AAA units during World War II.

Occasional passing references to a third computing sight, the Peca sight, are found. This sight was developed in North Africa during early 1943 through the inspiration of Lt. Col. Peter S. Peca, then CO of the 103d Coast Artillery Battalion (AA) Separate. The innovative Col. Peca would later become Antiaircraft Officer of V Corps.

I have recently been provided with photos and primary documents relating to the Peca sight. It is the first solid information I have encountered on this sight and it tells a fascinating story. The sight's potential was not lost on the Allied Force AA Officer, Col. Aaron Bradshaw, who ordered the design to be produced locally in a quantity sufficient for testing under North African combat conditions. Unfortunately, the story of the Peca sight seems to have a somewhat abrupt ending.

The Antiaircraft Artillery Board (AAAB) supposedly evaluated at length all known types of on-carriage sights before settling on the Weissight in May 1943 (Cibula 1946). Col. Peca was eventually informed by the Antiaircraft Command that his sight was rejected due to its fragility (Semmens 2004). This is curious, since one of the design criteria for the Peca sight was to produce a device that was “of rugged and sturdy construction.” Peca's design team was also aware of the instability and lack of ruggedness inherent in the Stiffkey Stick.

As I begin my examination of the Peca sight, several questions come to mind. Was the Peca sight given a fair evaluation by the AAAB? Considering that a prototype of the design was not ordered to be shipped to the States until late March 1943, was the standardization of the Weissight several weeks later already a fait accompli? Since H.K. Weiss was employed by the AAAB, was the Board too heavily invested in his design? Would the further development of the Peca sight have engendered some resentment on the part of the British if it outperformed the Stiffkey? Often such questions cannot be definitively answered at this late date. However, the topic is one well worth investigating. The work of Col. Peca and all involved in his project should be remembered and preserved.